At 11:26 AM 5/30/02 -0400, Peter F. Patel-Schneider wrote:
>From: Dan Brickley <danbri@w3.org>
> > RDFCore 1.0 RDF/XML documents have propositional content; they represent
> > 'claims about the world'. What factors fix this content, ie. what
> > is relevant when we set about considering whether some bundle of these
> > RDF/XML-represented propositions are true or not?
>
>Hmm, this is not really what I was getting at, as it includes lots of
>issues about the relationship between RDF graphs and the real world.
>
>I'm only interested in relationships between RDF graphs. Which such
>relationships are RDF relationships?
>
>My view is that the only such relationships are RDF entailment and RDFS
>entailment. Any agent that computes any other relationship between RDF
>graphs is not doing RDF.
It sure seems there is confusion about what it means to "do RDF". I agree
with you that many agent functions that have been mooted go beyond what is
licensed by RDF-entailment. It's difficult to imagine RDF being useful if
RDF-entailment is all that agents can do.
I think the importance of RDF entailment is not so much in what agents do
in the privacy of their stores, but in what they exchange between each
other. If agent A passes to agent B an RDF graph, then agent B may use
only RDF-entailments based on that graph as premises to its own reasoning
if those premises are to be presented as authorized by A. This does not,
of itself, prevent agent B from issuing further statements that have been
deduced using rules not sanctioned by RDF, and I agree that it would be
fair to say that in deducing such statements it is not doing sound RDF
reasoning.
But that doesn't seem to mean that they cannot be part of a useful network
of applications that use RDF to exchange information. So it seems that we
do need to be clearer about what it means to "do" RDF. For me, it is that
applications use RDF to exchange information in a fashion that has some
useful, widely recognized properties that go beyond just syntax.
So, coming round to things like rdfs:comment - yes, I agree it's important
to be careful not to claim that the object of this property affects the RDF
entailments than can be supported by a graph, but that doesn't mean there
are not other ways, outside RDF, in which information can be extracted from
the object value.
#g
-------------------
Graham Klyne
<GK@NineByNine.org>